Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0029463 (osteosarcoma)
 16,637 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cellular mechanism by which PTH and other osteotropic substances stimulate bone resorption is unclear. One hypothesis is that PTH-stimulated osteoblasts release cytokines which activate osteoclasts or osteoclast precursors. To examine whether cytokines are released by osteoblast-like cells in vitro, medium conditioned by a clonal rat osteosarcoma cell line 17/2.8 (ROS) was examined for mitogenic activity using a helper T lymphocyte line HT-2. This line proliferates in response to interleukin-2 (IL-2), IL-4, and granulocyte-macrophage colony-stimulating factor (GM CSF). Conditioned medium (CM) from untreated ROS cells caused proliferation of HT-2 cells. Treatment of ROS cells with PTH or lipopolysaccharide (LPS) caused a dose-dependent increase in the secretion of this mitogenic activity. To further define the nature of this mitogenic activity, we examined the effect of incubation of CM with neutralizing antibodies to IL-2, IL-4, and GM CSF. Mitogenic activity induced by both PTH- and LPS-treated ROS cell CM was completely inhibited by anti-GM CSF antibody, whereas there was no reduction in activity in the presence of antibodies to IL-2 or IL-4. Partial purification of both PTH- and LPS-treated CM using reverse phase HPLC resulted in a single peak of HT-2 mitogenic activity, which in both cases was completely inhibited by anti-GM CSF antibody. These findings suggest that PTH- and LPS-treated ROS cells secrete a T cell mitogenic activity which, by functional, serological, and biochemical criteria, is indistinguishable from GM CSF.
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PMID:Osteoblast-like cells secrete granulocyte-macrophage colony-stimulating factor in response to parathyroid hormone and lipopolysaccharide. 264 12

A highly sensitive bioassay for PTH was developed by using rat osteosarcoma cells (ROS 17/2.8). By limiting dilution, ROS cells were subcloned and the subclonal cell line (ROS 17/2.8-5) most responsive to PTH was selected. When subconfluent ROS 17/2.8-5 cells were treated with hydrocortisone for 3 days and then incubated with PTH, the cAMP response was significant at 10-40 ng/l hPTH (1-34) (4 approximately 16 X 10(-12) mol/l). Osteoclast activating factors such as human interleukin 1 alpha and beta, and tumour necrosis factor alpha did not stimulate cAMP production, whereas a conditioned medium of oesophageal carcinoma cells established from a patient with humoral hypercalcaemia stimulated cAMP production. By selecting PTH-responsive subclonal cells and treating them with hydrocortisone, the sensitivity for detecting PTH was improved approximately 15 times. This method will be useful in the characterization and purification of PTH-like factors produced by malignant tumours from hypercalcaemic patients.
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PMID:A highly sensitive bioassay for PTH using ROS 17/2.8 subclonal cells. 282 16

PTH receptors on two stable clonal rat osteosarcoma cell lines, ROS 17/2 and ROS 17/2.8, were characterized using an HPLC-purified, synthetic, sulfur-free, radioiodinated analog of bovine PTH, [Nle8,Nle18,Tyr,34]bovine PTH-(1-34)amide. PTH binding is specific for PTH agonists and antagonists and is dependent on the time and temperature of incubation. There is an excellent correlation between binding affinities of PTH agonists and antagonists in these intact cell systems with those in canine renal membranes. Peptides unrelated to PTH do not bind. Both ROS 17/2 and 17/2.8 have a single class of saturable, high affinity PTH binding sites that, by kinetic analysis and Scatchard analysis of saturation and competition studies, has a dissociation constant (Kd) of 0.8-1.4 nM. Bmax is approximately 36,000 and 72,000 sites per cell in ROS 17/2 and 17/2.8, respectively. A close correlation was found between the binding of PTH agonists to their receptors in ROS 17/2 cells with their relative biological potencies as measured by stimulation of adenylate cyclase in plasma membranes prepared from these cells. Prolonged treatment of ROS 17/2 and 17/2.8 cells with PTH agonists results in a dose- and time-dependent decrease of available cell-surface binding sites, without alterations in Kd. PTH antagonists do not regulate PTH receptors. Regulation of PTH receptors by PTH agonists is dependent on the dose and time of exposure to ligand over a dose range of 10(-8) to 10(-11) M. Cells exposed to agonists (greater than or equal to 10(-8) M) for 48 h show maximally decreased receptor number; continued exposure to agonists (greater than or equal to 10(-8) M) does not further decrease PTH receptor number, which remains constant at about 15% of control values. Agonist-induced down-regulation occurs with less than 10(-11) M agonists, a concentration less than 10% of the minimal dose detected by direct ligand competition. Treatment of ROS 17/2 cells with PTH agonists results in a dose- and time-dependent decrease of PTH-stimulated adenylate cyclase. This agonist-induced desensitization correlates closely with the decreased availability of PTH receptors: it is maximal in cells exposed to agonists (greater than 10(-8) M) for 48 h and also does not decrease further with continued exposure of the cells to agonist. Future studies with these stable ROS cell lines should permit detailed analysis of the biochemical mechanisms underlying homologous and heterologous regulation of PTH receptors and desensitization and sensitization of the adenylate cyclase response.
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PMID:Characterization and agonist-induced down-regulation of parathyroid hormone receptors in clonal rat osteosarcoma cells. 283 Oct 22

The N-terminal fragment of human hypercalcemia factor (hHCF), hHCF-(1-34)NH2, has bioactivities similar to PTH in vitro and in vivo. Because it interacts with PTH receptors and is more potent than PTH in some systems, the hHCF sequence may provide interesting leads for the design of potent and selective PTH and hHCF antagonists. Based on the antagonist activity of [Tyr34]bovine PTH-(7-34)NH2 [( Tyr34]bPTH-(7-34)NH2), we synthesized the corresponding fragment of hHCF, hHCF-(7-34)NH2 and examined its properties in vitro. In the bone-derived rat osteosarcoma cell line ROS 17/2.8, hHCF-(7-34)NH2 and [Tyr34]bPTH-(7-34)NH2 were equipotent for inhibition of radiolabeled PTH-binding. In contrast, hHCF-(7-34)NH2 was 8-fold more potent that [Tyr34]bPTH-(7-34)NH2 for inhibiting PTH-stimulated cAMP production. hHCF-(7-34)NH2 also inhibited PTH-binding and PTH-stimulated adenylate cyclase activity in bovine renal cortical membranes: hHCF-(7-34)NH2 and [Tyr34]bPTH-(7-34)NH2 were equipotent in this system. In addition, hHCF-(7-34)NH2 antagonized hHCF-(1-34)NH2 action in both systems with similar inhibition constants. However, unlike the PTH analogue, hHCF-(7-34)NH2 (8 microM) was a weak partial agonist, producing a 2.4-fold increase in cAMP (5% of the maximal response) in ROS cells. This same system also detects agonism for [Nle8, 18Tyr34]bPTH-(3-34)NH2, another PTH partial agonist/antagonist. These results demonstrate that hHCF-(7-34)NH2 interacts with PTH receptors based in large part on the region which is not homologous to PTH, and suggest the utility of the ROS 17/2.8 cell system for identifying weak agonism of PTH and hHCF analogues in vitro.
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PMID:The 7-34-fragment of human hypercalcemia factor is a partial agonist/antagonist for parathyroid hormone-stimulated cAMP production. 283 81

We characterized the alkaline phosphatase activity of the human osteogenic sarcoma cell line, SAOS-2, and studied the regulation of this enzyme and 3',5'-cyclic adenosine monophosphate levels by 1,25-dihydroxyvitamin D3 and triamcinolone acetonide. We report that the basal alkaline phosphatase activity of SAOS-2 cells was 100-1000 times greater than that of other established human osteogenic sarcoma cell lines. The enzymatic activity was thermolabile, could be inhibited by levamisole and L-homoarginine, but not by L-phenylalanine, and was immunoprecipitable with anti-bone/liver/kidney, but not with anti-placental antibody, confirming that it is the tissue-unspecific or bone/liver/kidney isoenzyme. However, in contrast to other established human osteosarcoma cell lines (TE-85, SAOS-1), in which alkaline phosphatase activity is stimulated several-fold by the steroid hormones 1,25-dihydroxyvitamin D3 and hydrocortisone, the alkaline phosphatase activity of SAOS-2 cells was not affected by 1,25-dihydroxyvitamin D3 treatment despite the presence of classical receptors for this hormone. Furthermore, administration of the potent glucocorticoid analogue, triamcinolone acetonide, induced only a modest increase in activity. The SAOS-2 cell line expressed low basal cAMP levels (28 pmol/10(6) cells) which could be increased 25-40 times by pretreatment with parathyroid hormone. However, unlike other osteoblastic models, in which PTH-induced cAMP stimulation is modulated by 1,25-dihydroxyvitamin D3 and glucocorticoids, neither of these hormones had an effect on the PTH-stimulated cAMP levels in SAOS-2 cells. We conclude that the SAOS-2 cell line is an osteoblastic cell model which expresses high levels of tissue-unspecific alkaline phosphatase activity and exhibits limited responsiveness to two steroid hormones.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of a human osteoblastic osteosarcoma cell line (SAOS-2) with high bone alkaline phosphatase activity. 284 3

1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) receptor content in cultured osteogenic sarcoma cells (UMR-106) was found to be increased after treatment with both bovine and human PTH and human PTH-like peptide (hPLP). The dose dependent increase of receptors was preceded by a dose dependent stimulation of cAMP production. This suggests a role for cAMP as mediator of the PTH- and hPLP-induced 1,25-(OH)2D3 receptor up-regulation. Furthermore, evidence was obtained that new mRNA and de novo receptor synthesis is involved in this heterologous 1,25-(OH)2D3 receptor up-regulation.
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PMID:Heterologous up-regulation of the 1,25-dihydroxyvitamin D3 receptor by parathyroid hormone (PTH) and PTH-like peptide in osteoblast-like cells. 284 85

We compared the bioactivities of a synthetic truncated NH2-terminal fragment of the human (h) PTH-like peptide (PLP) associated with malignancies [hPLP-(3-34)], an intact NH2-terminal fragment [hPLP-(1-34)], and an NH2-terminal fragment of PTH [hPTH-(1-34)]. Although hPLP-(1-34) was less potent than hPTH-(1-34) in stimulating adenylate cyclase in rat renal membranes, hPLP-(1-34) and hPTH-(1-34) were equipotent in stimulating adenylate cyclase in OK renal cells as well as in UMR 108 osteosarcoma cells in vitro. In osteosarcoma cells, each of these peptides could desensitize adenylate cyclase responses to itself and to the other peptide, but could not reduce stimulation by prostaglandin E2. Renal membranes of vitamin D-deficient rats with secondary hyperparathyroidism had a reduced PLP-stimulated as well as PTH-stimulated adenylate cyclase response. The truncated analog hPLP-(3-34) was only a weak partial agonist and an antagonist in vitro, produced equivalent inhibition of hPLP-(1-34) and hPTH-(1-34) in renal and osseous cells, and could not desensitize agonist responses. In thyroparathyroidectomized rats in vivo, hPLP-(1-34) and hPTH-(1-34) increased cAMP excretion, enhanced phosphaturia, maintained plasma calcium, and reduced calciuria. Equimolar concentrations of hPLP-(3-34) produced no increases above control levels; however, high concentrations of this peptide mimicked PTH actions on renal and plasma ion handling while modestly augmenting cAMP excretion. These results demonstrate the importance of the first two residues of PLP for bioactivity, indicate that PLP and PTH interact at common receptor sites in vivo as well as in vitro, suggest that PLP may not be less potent than PTH in renal target cells, and indicate that the net result of interaction of these peptides with their common receptor in target tissues may reflect both activation and desensitization of receptor-mediated events.
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PMID:Influence of the amino-terminus on in vitro and in vivo biological activity of synthetic parathyroid hormone-like peptides of malignancy. 284 83

Human PTH-related protein (hPTHrP) has been characterized as a product of tumor cells with sequence homology to the biologically active amino-terminal portion of human PTH (hPTH). We measured the relative activities of synthetic amino-terminal sequences of hPTH-(1-34) and hPTHrP-(1-34) to stimulate production of cAMP in intact human SaOS-2 osteosarcoma cells. Both peptides enhanced cAMP production at concentrations of 2.5-7.5 X 10(-10) M, had parallel dose-response curves, and were of essentially equal potency. Preincubation of SaOS-2 cells with hPTH-(1-34) or hPTHrP-(1-34) for 1 or 4 h induced homologous desensitization to a second challenge with the same peptide as well as heterologous desensitization to the other PTH peptide, but had little or no effect on the action of vasoactive intestinal peptide; the magnitudes of homologous and heterologous desensitization induced by the same doses of hPTHrP-(1-34) or hPTH-(1-34) were similar. Bone resorption-stimulating activity was measured using 40Ca2+ release from neonatal mouse calvariae in organ culture after 72 h of incubation. hPTHrP-(1-34) gave a dose-response between 0.2 and 5 ng/ml (5 X 10(-11) and 1.2 X 10(-9) M), was about 3 times more potent than Lilly bovine PTH standard (assuming a SA of 3000 U/mg; 100 U/ml), gave the same maximum response as hPTH-(1-34), and was 20-30% as potent as hPTH-(1-34). Neither hPTH-(1-34) nor hPTHrP-(1-34) enhanced prostaglandin production in mouse calvariae, and indomethacin did not inhibit the bone resorption-stimulating activities of either peptide. We conclude that hPTHrP-(1-34) and hPTH-(1-34) have similar high specific biological activities to stimulate production of cAMP in human osteoblast-like cells, but that hPTHrP-(1-34) is modestly less potent than hPTH-(1-34) to stimulate bone resorption in mouse calvariae.
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PMID:Human parathyroid hormone (PTH)-related protein and human PTH: comparative biological activities on human bone cells and bone resorption. 284 88

We identified the subunits of the stimulatory and inhibitory guanine nucleotide binding proteins (Gs and Gi, respectively) associated with adenylate cyclase in rat osteosarcoma (ROS) cells. Pertussis toxin catalyzed ADP-ribosylation of Gi alpha in ROS cells increased agonist (PTH and isoproterenol)-stimulated, but not basal, cAMP production. The effect of pertussis toxin was dose and time dependent, and slowly reversible (T 1/2 approximately 30 h) during continued culture without toxin. Pertussis toxin treatment of ROS cell lines (17/2.8 and 24/l) with markedly different agonist responsiveness increased agonist-stimulated cAMP production in proportion to the response without toxin treatment. Pertussis toxin treatment further increased cAMP response to PTH in dexamethasone treated cells. We conclude that ROS cells contain functional Gi which modulates agonist-stimulated cAMP formation. Alterations in ROS cAMP responsiveness caused by steroids, and the reduced responsiveness of the 24/1 cell line, however, are unlikely to be due to changes in Gi.
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PMID:The inhibitory guanine nucleotide regulatory protein modulates agonist-stimulated cAMP production in rat osteosarcoma cells. 285 47

We have investigated the actions of 17 beta-estradiol (E2) on the production of cAMP stimulated by synthetic human PTH [hPTH-(1-34)], synthetic hPTH-related protein [hPTHrP-(1-34)], and vasoactive intestinal peptide (VIP) in human (SaOS-2) and rat (ROS 17/2.8) osteoblast-like osteosarcoma cells. In SaOS-2 cells, hPTH-(1-34) (2.5 nM), hPTHrP-(1-34) (2.5 nM), and VIP (10-100 nM) stimulated the accumulation of cAMP markedly (greater than 20- to 30-fold in 1 h). Cells were preincubated in serum-free medium for 4-24 h, then in the absence or presence of E2 for 4 h before a 1-h stimulation with peptide hormone in the absence of E2. In SaOS-2 cells, pretreatment with E2 (10(-12)-10(-8) M) for 4 h inhibited by up to 50% the accumulation of cAMP stimulated by hPTH-(1-34) or hPTHrP-(1-34), but E2 had no inhibitory effect on VIP action. 17 alpha-Estradiol had no inhibitory action on hPTH- or hPTHrP-stimulated accumulation of cAMP at concentrations as high as 10(-8) M. Additional evidence against a nonspecific effect of E2 was the total lack of inhibition of cAMP accumulation stimulated by hPTH-(1-34) or hPTHrP-(1-34) in ROS 17/2.8 cells at concentrations of E2 up to 10(-6) M. We conclude that E2 can act directly and rapidly in human osteoblast-like cells to modulate selectively the ability of hPTH and hPTHrP to enhance the production of cAMP.
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PMID:Direct modulation by estradiol of the response of human bone cells (SaOS-2) to human parathyroid hormone (PTH) and PTH-related protein. 290 73


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